JPS6230557Y2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a high-speed boat equipped with a screw propeller at the stern.

In a conventional high-speed boat, as shown in FIG. 1, a propeller shaft 5 extending downwardly from the main engine 2 in the stern section of the hull 1 is connected to shaft brackets 4a and 4b under the bottom of the boat. The flow entering the screw propeller 3 at the rear end of the propeller shaft 5 has a considerable diagonal angle α. In addition, the code|symbol 6 in a figure shows a rudder, and 7 shows a still water surface.

When the screw propeller 3 operates in such a mixed flow state, the angle of attack of the flow relative to the propeller blades changes in the circumferential direction. This caused severe cavitation, which caused problems such as hull vibration, damage to the bottom shell, and cavitation and erosion of the propeller blade root.

Furthermore, since the direction of the thrust force T of the screw propeller 3 is different from the traveling direction, the effective thrust force for moving the hull 1 forward is T·cos α, which is smaller than the thrust force T generated by the screw propeller 3.

Therefore, in order to reduce the above-mentioned diagonal flow angle α, high-speed boats as shown in Figs.
A skeg 9 is provided in a protruding manner, and a screw propeller 3 is provided on the rear side thereof.

In this way, by housing the screw propeller 3 in the tunnel section 8 on the bottom of the ship, navigation in shallow water becomes possible, but on the other hand, it is difficult to slide on the bottom surface of the ship at high speeds, and the screw propeller Since the flow of water flowing into the vessel 3 passes through the stern tunnel section 8 from the bow side, the inside of this stern tunnel section 8 is always filled with water.

Therefore, there is a problem in that the resistance due to the inner surface of the stern tunnel section 8 and the skeg 9 is large, and the resistance becomes very large especially in high speed ranges, requiring the main engine 2 with a high output.

In view of the above-mentioned points in conventional high-speed boats, the present invention prevents troubles such as erosion by making the flow flowing into the screw propeller almost parallel to the propeller axis, and at the same time keeps the screw propeller in a semi-submerged state. To provide a high-speed boat, which improves propeller efficiency in a high-speed range by operating the propeller at high-speed range, and maintains the characteristics of facilitating the hull planing in a high-speed range while maintaining sufficient steering. purpose.

Therefore, in the high-speed boat of the present invention, a bottom recess that opens downward and rearward is formed at the stern end from below the water surface to above the water surface, and a bottom stepped portion having an end wall is formed at the front end of the bottom recess. A propeller shaft driven by the main engine inside the ship extends rearward and is arranged to pass near the bottom of the bottom step, and the screw propeller at the rear end of the propeller shaft extends only its upper half to the bottom of the ship. It is characterized in that it is disposed so as to be housed in the recess, and that rudders are provided vertically on the left and right bottoms of the bottom recess.

Hereinafter, a high-speed boat as an embodiment of the present invention will be explained with reference to the drawings. FIG. 5 is a side view showing the main parts cut away, FIG. 6 is a sectional view taken along the - arrow in FIG. 5, and FIG. 5 is a cross-sectional view taken along the - arrow in FIG. 5, FIG. 8 is a side view corresponding to FIG. 5 and shows the high-speed navigation state, FIG. It is a graph showing propeller efficiency corresponding to the boat speed of a high-speed boat.

As shown in FIGS. 5 to 7, a bottom recess 10 that opens downward and rearward at the stern end of the hull 1
is formed from below to above the water surface 7.

An end wall 10a is provided at the front end of this bottom recess 10.
A propeller shaft 5 driven by the main engine 2 inside the ship extends rearward and is disposed so as to pass near the bottom of the bottom step.

Therefore, the screw propeller 3 at the rear end of the propeller shaft 5 is arranged such that only its upper half is housed inside the bottom recess 10.

Furthermore, rudders 6a and 6b are vertically installed on the left and right bottom portions of the bottom recess 10, respectively. In addition, the code|symbol 7 in a figure shows a still water surface.

As mentioned above, since the upper half of the screw propeller 3 is housed in the bottom recess 10, the angle of inclination of the propeller shaft 5 is smaller than in the conventional case shown in FIG. The angle of diagonal flow of the water flowing into the propeller 3 also becomes smaller.

Further, since most of the propeller shaft 5 is disposed inside the ship, there is no need for a shaft bracket.

Note that the bottom stepped portion having the end wall 10a of the bottom recess 10 is formed just in front of the screw propeller 3.

When the flow of water flowing into the screw propeller 3 has a smaller diagonal flow angle than in the conventional case shown in FIG. 1, the screw propeller 3 operates in a substantially uniform flow.

Therefore, cavitation in mixed flow conditions that occurs in conventional screw propellers of high-speed boats is sufficiently prevented, and cavitation/erosion at the propeller blade root, hull vibration,
This prevents damage to the bottom shell. Furthermore, since the direction of the propeller thrust force T substantially coincides with the forward direction of the hull 1, there is an advantage that loss of thrust force is reduced.

Furthermore, the propeller shaft 5 is not exposed to the outside of the hull 1, and the shaft bracket (reference numerals 4a and 4 in FIG.
(see b), there is also the advantage that the resistance caused by these additives is eliminated.

In the high-speed boat of the present invention, the bottom recess 10 on the rear side of the bottom step is formed up to above the water surface, so it can plan without any trouble during high-speed sailing. As shown, the water along the bottom of the ship is cut off by the bottom step in front of the screw propeller 3, and the water surface becomes 1.
It becomes as shown in 1.

In this way, the screw propeller 3 operates in a semi-submerged state, but generally at high speeds, as shown in Figure 10, the screw propeller 3 operates in a semi-submerged state (graph A). The propeller efficiency is higher than that of a fully submerged screw propeller (graph B), so the high-speed boat of this invention can achieve greater boat speed than the conventional case with the same main engine horsepower. It will be done.

Furthermore, in the high-speed boat of the present invention, the rudders 6a and 6b are vertically installed on the left and right bottom parts of the bottom recess 10, so these rudders 6a and 6b are always underwater, and even when sailing at high speed, the screw propeller 3 The bubble mixture flow generated by this will not flow in, and therefore, deterioration in steering can be prevented.

As described in detail above, according to the high-speed boat of the present invention, the screw propeller is disposed so that only its upper half is housed in the hull recess on the rear side of the bottom step, and It has a simple structure with rudders installed vertically on the left and right bottom of the ship.
In addition to preventing cavitation/erosion at the propeller blade root and hull vibration, loss of propeller thrust is reduced, and the hull skies effectively at high speeds, resulting in high propeller efficiency and the rudder. This also prevents hearing loss.

[Brief explanation of the drawing]

Fig. 1 is a side view of the stern part of an example of a conventional high-speed boat, and Figs. 2 to 4 show other examples of the conventional high-speed boat, with Fig. 2 being a side view of the stern part thereof, and Fig. 3 FIG. 4 is a sectional view taken along the - arrow in FIG. 2, FIG. 4 is a sectional view taken along the - arrow in FIG. 6 is a sectional view taken along the - arrow of FIG. 5, FIG. 7 is a sectional view taken along the - arrow of FIG. 5, and FIG. A side view showing its high-speed navigation state, Figure 9 is the same as Figure 8.
FIG. 10 is a sectional view taken in the direction of arrows, and is a graph showing the propeller efficiency corresponding to the boat speed of the high-speed boat. 1... Hull, 2... Main engine, 3... Screw propeller, 5... Propeller shaft, 6a, 6b... Rudder,
7... Still water surface, 10... Bottom recess, 10a... End wall, 11... Water surface during high speed navigation, T... Thrust.

Claims (1)

[Scope of utility model registration request] A bottom recess that opens downward and rearward at the stern end is formed from below the water surface to above the water surface, and a bottom stepped portion having an end wall is formed at the front end of this bottom recess, and a propeller driven by the main engine inside the ship. The shaft is arranged so as to extend rearward and pass near the lower part of the bottom step, so that only the upper half of the screw propeller at the rear end of the propeller shaft is housed in the bottom recess. 1. A high-speed boat, characterized in that rudders are provided vertically on the left and right bottoms of the bottom recess.